Ultrasound guided interscalene nerve blocks for perioperative analgesia can be safely and effectively performed in the obese patient but they may be more difficult to perform and analgesia may not be as complete.

Background and objectives: Obese patients can pose a unique perioperative anesthetic challenge, making regional anesthetic techniques an intriguing means of providing analgesia for this population. Ultrasound guidance has been touted recently as being beneficial for this population in which surface landmarks can become obscured. In this study, the effect of increased Body Mass Index (BMI) on ultrasound guided interscalene peripheral nerve blockade is investigated. Material and methods: This study is a retrospective review of 528 consecutive patients who received preoperative ultrasound-guided interscalene nerve blocks at the University of Wisconsin Hospital and Clinics. We examined the association between BMI and the following parameters: time required for block placement; presence of Postoperative Nausea and Vomiting (PONV); postoperative Post Anesthesia Care Unit (PACU) pain scores; volume of local anesthetic injected; acute complications; and opioid administration preoperatively, intraoperatively, and postoperatively. Univariate and multivariate least squares and logistic regression models were used. Results: An elevated BMI was associated with an increased: time required for block placement (p-value = 0.025), intraoperative fentanyl administration (p-value < 0.001), peak PACU pain scores (p-value < 0.001), PACU opioid administration (p-value < 0.001), PACU oral opioid administration (p-value < 0.001), total PACU opioid administration (p-value < 0.001) and incidence of PACU nausea (p-value = 0.025) Conclusions: Ultrasound guided interscalene nerve blocks for perioperative analgesia can be safely and effectively performed in the obese patient but they may be more difficult to perform and analgesia may not be as complete.

The goal of this study was to determine the age‐induced changes in antioxidant and pro‐oxidant status in skeletal muscle. Contracting skeletal muscle is ripe for production of reactive oxygen species, which may contribute to impaired muscle blood flow in older adults by overwhelming NO signaling in arteries. We hypothesized that muscle from older humans would exhibit reduced levels of antioxidant proteins and increased levels of pro‐oxidant proteins. A muscle biopsy was taken from the vastus lateralis muscle in young (18–40 yrs) and older (65–77 yrs) subjects. Muscle fibers were homogenized, adjusted for equal concentrations, and we assessed protein expression via Western blot and ECL. Proteins of interest were superoxide dismutase (SOD‐1, SOD‐2), catalase, and xanthine oxidase (XO). Probing for nitrotyrosine served as a marker for protein oxidative stress. Preliminary results (young n=3, older n = 5) showed that catalase expression was higher in young adults (P=0.04) while SOD‐1 levels were approximately equal. SOD‐2 levels were greater in older adults (P=0.01) as were nitrotyrosine levels. XO levels tended to be higher in the older adult group (P=0.07). These data suggest that aging skeletal muscle shows increased oxidative stress in parallel with lower catalase and higher XO and nitrotyrosine levels. This may ultimately lead to a decrease in NO bioavailability in aging human skeletal muscle during exercise. Funded by the Wisconsin Alumni Research Foundation (WARF).